From: Jason Gunthorpe <jgg@ziepe.ca>
To: Samiullah Khawaja <skhawaja@google.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>,
David Woodhouse <dwmw2@infradead.org>,
Lu Baolu <baolu.lu@linux.intel.com>,
Joerg Roedel <joro@8bytes.org>, Will Deacon <will@kernel.org>,
iommu@lists.linux.dev, YiFei Zhu <zhuyifei@google.com>,
Robin Murphy <robin.murphy@arm.com>,
Pratyush Yadav <pratyush@kernel.org>,
Kevin Tian <kevin.tian@intel.com>,
linux-kernel@vger.kernel.org, Saeed Mahameed <saeedm@nvidia.com>,
Adithya Jayachandran <ajayachandra@nvidia.com>,
Parav Pandit <parav@nvidia.com>,
Leon Romanovsky <leonro@nvidia.com>, William Tu <witu@nvidia.com>,
Vipin Sharma <vipinsh@google.com>,
dmatlack@google.com, Chris Li <chrisl@kernel.org>,
praan@google.com
Subject: Re: [RFC PATCH 13/15] iommufd: Persist iommu domains for live update
Date: Fri, 3 Oct 2025 09:09:36 -0300 [thread overview]
Message-ID: <20251003120936.GN3195829@ziepe.ca> (raw)
In-Reply-To: <CAAywjhS77-Kw7GVgksimZ8-Oy+kSvCPpL8xQfJt0eQHwf=WH_g@mail.gmail.com>
On Thu, Oct 02, 2025 at 04:56:57PM -0700, Samiullah Khawaja wrote:
> > So if you have a notion that finish is disallowed and when it is
> > actually finished maybe the order doesn't matter?
>
> I think FINISH for FDs in a SESSION is not atomic. If a dependency
> memfd gets its FINISH call first, it might make itself mutable before
> the iommufd FINISH callback fails because old HWPT is not replaced
> yet. By then, it would be too late; the memfd has already become
> mutable. That is why order would be needed.
I'm thinking of having an counter in the session and the iommu_domain
holds it elevated until it is destroyed. Finish can't even start until
the counter is 0.
If the counter is 0 then it is fine to unfreeze all the remaning
objects in any order.
Jason
next prev parent reply other threads:[~2025-10-03 12:09 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-28 19:06 [RFC PATCH 00/15] iommu: Add live update state preservation Samiullah Khawaja
2025-09-28 19:06 ` [RFC PATCH 01/15] iommu/vt-d: Register with Live Update Orchestrator Samiullah Khawaja
2025-09-28 19:06 ` [RFC PATCH 02/15] iommu: Add rw_semaphore to serialize live update state Samiullah Khawaja
2025-09-28 19:06 ` [RFC PATCH 03/15] iommu/vt-d: Prevent hotplugs when live update state is not normal Samiullah Khawaja
2025-09-29 15:51 ` Jason Gunthorpe
2025-09-29 16:50 ` Pasha Tatashin
2025-09-29 17:21 ` Samiullah Khawaja
2025-09-28 19:06 ` [RFC PATCH 04/15] iommu: Add preserve iommu_domain op Samiullah Khawaja
2025-09-28 19:06 ` [RFC PATCH 05/15] iommu: Introduce API to preserve iommu domain Samiullah Khawaja
2025-09-29 15:54 ` Jason Gunthorpe
2025-09-29 18:11 ` Samiullah Khawaja
2025-09-28 19:06 ` [RFC PATCH 06/15] iommu/vt-d: Add stub intel iommu domain preserve op Samiullah Khawaja
2025-09-28 19:06 ` [RFC PATCH 07/15] iommu/vt-d: Add implementation of live update prepare callback Samiullah Khawaja
2025-09-28 19:06 ` [RFC PATCH 08/15] iommu/vt-d: Implement live update preserve_iommu_context Samiullah Khawaja
2025-09-29 15:57 ` Jason Gunthorpe
2025-09-28 19:06 ` [RFC PATCH 09/15] iommu/vt-d: Add live update freeze callback Samiullah Khawaja
2025-09-29 15:58 ` Jason Gunthorpe
2025-09-28 19:06 ` [RFC PATCH 10/15] iommu/vt-d: Restore iommu root_table and context on live update Samiullah Khawaja
2025-09-28 19:06 ` [RFC PATCH 11/15] iommufd: Add basic skeleton based on liveupdate_file_handle Samiullah Khawaja
2025-09-28 19:06 ` [RFC PATCH 12/15] iommufd-luo: Implement basic prepare/cancel/finish/retrieve using folios Samiullah Khawaja
2025-09-28 19:06 ` [RFC PATCH 13/15] iommufd: Persist iommu domains for live update Samiullah Khawaja
2025-09-29 16:00 ` Jason Gunthorpe
2025-09-29 17:32 ` Samiullah Khawaja
2025-09-29 17:43 ` Jason Gunthorpe
2025-09-29 17:45 ` Pasha Tatashin
2025-09-30 13:07 ` Pasha Tatashin
2025-09-30 13:59 ` Jason Gunthorpe
2025-09-30 15:09 ` Pasha Tatashin
2025-09-30 16:31 ` Jason Gunthorpe
2025-09-30 20:02 ` Samiullah Khawaja
2025-09-30 21:05 ` Jason Gunthorpe
2025-09-30 23:15 ` Samiullah Khawaja
2025-10-01 11:47 ` Jason Gunthorpe
2025-10-01 19:28 ` Pasha Tatashin
2025-10-02 11:57 ` Jason Gunthorpe
2025-10-02 14:43 ` Pasha Tatashin
2025-10-02 15:10 ` Jason Gunthorpe
2025-10-02 19:29 ` Samiullah Khawaja
2025-10-02 21:12 ` Jason Gunthorpe
2025-10-02 21:30 ` Pasha Tatashin
2025-10-02 22:58 ` Jason Gunthorpe
2025-10-02 23:56 ` Samiullah Khawaja
2025-10-03 12:09 ` Jason Gunthorpe [this message]
2025-10-02 1:00 ` Samiullah Khawaja
2025-10-02 13:41 ` Jason Gunthorpe
2025-10-02 14:59 ` Pasha Tatashin
2025-10-02 17:03 ` Samiullah Khawaja
2025-10-02 17:37 ` Jason Gunthorpe
2025-10-02 18:08 ` Samiullah Khawaja
2025-10-10 1:28 ` Pasha Tatashin
2025-10-10 14:24 ` Jason Gunthorpe
2025-09-28 19:06 ` [RFC PATCH 14/15] iommu/vt-d: sanitize restored root table and iommu contexts Samiullah Khawaja
2025-09-28 19:06 ` [RFC PATCH 15/15] iommufd/selftest: Add test to verify iommufd preservation Samiullah Khawaja
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